In the manufacture of industrial containers, particularly in the manufacture of steel drums, it has been long been the practice to provide the container a closure construction adapted to be closed by a closure member or cap, by mechanically securing within an opening formed in a wall of the container such as the end wall of a drum or barrel, an annular flange member having a radially extending flange portion and a previously helically threaded axially extending portion adapted to receive a threaded closure cap. Such a flange member should be firmly secured in the container wall so that on threading or unthreading of the cap the flange member will not loosen or turn in the container wall, and so that there is no leakage between the container wall and the flange member that could permit fluid contents to leak out of the container or external fluid to leak into the container at such location.
The flange member has its helical thread formed prior to installation of the member in the wall to avoid the problems of cutting or otherwise forming the thread in the flange member after it is fixed in the container wall which usually it is large and would be difficult or impossible to mount in apparatus for accurately forming a thread.
In installing such a flange member in an opening in a container wall, such as the end wall of a steel drum, it has usually been the practice in the past either to crimp the metal of the container wall beneath as well as over the outer edge of radially extending flange portion of a flange member by substantial radial forces applied to the metal of the container wall, or to clamp the edge of the opening of the container wall between a separate auxiliary ring portion and radially and axially extending portions of a flange member. Other constructions have also been proposed.
In general, however, all of these methods of securing the flange member to the container wall involve the application of substantial lateral or radial forces to either the radially extending portion of the flange member or to the axially extending portion of the flange member to deform suitably the metal of the container wall to grip the flange member.
The application of such substantial radial or lateral forces in general usually do not provide substantial difficulties where the opening in the flange member is and container wall are of relatively small diameters such as the two-inch diameter opening commonly used in the flange members of closure constructions of steel drums, and where there is no need for a great degree of accuracy in the thread of the axial portion of the flange member because the threaded cap is manually applied or removed.
Moreover, for certain uses it has been found very desirable that it be possible to remove and replace the closure cap, without manual handling, from the threaded closure construction in a container.
For example, it is desirable in certain applications to package dangerous or toxic materials in closed containers, by remote control, without manual handling of the cap or without exposure of any human to the materials or emanations therefrom, by removing the cap from a container, holding the cap while the container has the material introduced into the container, and then threading the cap onto the closure construction and tightening the cap to form a tightly sealed closure, all without any manual handling of the cap.
To make this possible, it is necessary that there be a high degree of accuracy and freedom of distortion of the thread in the axially extending portion of the flange member of the closure construction, to permit such removal and replacement of the cap without manual handling.
Moreover, there has developed a need for containers such as steel drums with openings substantially larger than the two-inch diameter opening usually provided in ordinary steel drums. In some cases it is desired to have an opening four inches in diameter, or even larger; and in other cases to have the closure construction so designed with an accurate thread so that even if the opening is of such large diameter the closure cap can be unthreaded and removed from the opening then re-inserted and threaded at the opening by mechanical means, without manual handling.
It has been found in general that in the heretofore known methods and apparatus for installing flange members of closure constructions into walls of steel containers, the radial forces imposed on the flange member are so great as to distort the flange member and its previously formed thread sufficiently to prevent removal and replacement of the cap without manual handling, particularly if the flange member and the opening through it are of relatively large diameter, as on the order of four inches or more.
Heretofore, to the best of applicants' knowledge, none of the methods and apparatus heretofore known for installing flange members in the walls of metal containers such as steel drums, can be successfully used to install and secure a large diameter flange member having a large diameter opening into a container wall without harmful distortion from the forces applied to the flange member in installing and securing the flange member in the container wall.